Billboard GUI not always displayed?

Excuse the mess, but in the script I've made below. It saves the XP/Level etc of the player and loads it all up. But on some servers when people are playing my game, the Billboard Gui doesn't display above their heads with the Level of their player and on other servers the whole thing works fine.

I have noticed it has said Levels is not a valid Int occasionally but I'm sure that's no longer a problem.

local ds = game:GetService("DataStoreService"):GetDataStore("dataone1")
local dso = game:GetService("DataStoreService"):GetOrderedDataStore("levelstore1")

function PlayerAdded(newPlayer)

    local stats = Instance.new("IntValue", newPlayer)
    stats.Name = "leaderstats1"

     local coins = Instance.new("IntValue", stats) 
    coins.Name = "Coins"

    local tokens = Instance.new("IntValue", stats)
    tokens.Name = "Tokens"

    local xp = Instance.new("IntValue", stats)
    xp.Name = "XP"

    local levels = Instance.new("IntValue", stats)
    levels.Name = "Levels"

    local coinKey = ds:GetAsync("Key" .. newPlayer.Name) 
    if coinKey then
        coins.Value = coinKey
    else
        coins.Value = 0
    end

    local tokensKey = ds:GetAsync("Key1" .. newPlayer.Name)
    if  tokensKey then
        tokens.Value = tokensKey
    else
        tokens.Value = 0
    end
    local xpKey = ds:GetAsync("Key2" .. newPlayer.Name)
    if xpKey then
        xp.Value =xpKey
    else
        xp.Value = 0
    end
    local levelsKey = dso:GetAsync("" .. newPlayer.Name)
    if levelsKey then
        levels.Value = dso:GetAsync("" .. newPlayer.Name)    
    else
        levels.Value = 1
    end

        coins.Changed:connect(function(save)
            ds:SetAsync("Key" .. newPlayer.Name, save)
        end)
        tokens.Changed:connect(function(save)
            ds:SetAsync("Key1" .. newPlayer.Name, save)
        end)

    local xpDeb = false
        xp.Changed:connect(function()
        if xpDeb then return end
        xpDeb = true
        while xp.Value >= 100 do
            xp.Value = xp.Value - 100
            levels.Value = levels.Value + 1
        end
            ds:SetAsync("Key2" .. newPlayer.Name, xp.Value)
        dso:SetAsync("" .. newPlayer.Name, levels.Value)
        xpDeb = false
        end)
end

function CharacterAdded(newPlayer)
	wait(6)
	newPlayer.leaderstats1:WaitForChild("Levels")
    local gui=Instance.new("BillboardGui")
    gui.Parent=newPlayer.Character.Head
    gui.Adornee=newPlayer.Character.Head
    gui.Size=UDim2.new(3,0,2,0)
    gui.StudsOffset=Vector3.new(0,2,0)
    local text=Instance.new("TextLabel")    
	text.TextColor3 = Color3.new(255, 255, 255)
    text.Text = "Level " .. newPlayer.leaderstats1.Levels.Value
    text.Size=UDim2.new(1.25,0,0.5,0)
    text.Position=UDim2.new(-0.125,0,-0.25,0)
    text.BackgroundTransparency = 1
    text.Parent=gui
    text.FontSize = ("Size36")
    text.Font = ("SourceSansBold")
    
    text.TextStrokeColor3 = Color3.new(0.50, 0.50, 0.50)
    text.TextStrokeTransparency = 0
    w = game.Lighting.WepsGroup:GetChildren() 
    for i = 1,#w do
        w[i]:Clone().Parent = newPlayer.Backpack
    end
end


function onPlayerEntered(newPlayer) 
    newPlayer.Changed:connect(function (property) 
        if (property == "Character") then 
            CharacterAdded(newPlayer) 
        end 
    end) 
end 
game.Players.PlayerAdded:connect(onPlayerEntered) 
game.Players.PlayerAdded:connect(PlayerAdded)